What’s happening to our maples?

Asked October 18, 2019, 12:38 PM EDT

The maples have steadily looked worse this year, thinning on one side, seems to be happening in the entire neighborhood, any ideas? The maples run down an entire street.

Clackamas County Oregon trees and shrubs

4 Responses

Thank you for your question. Maple trees are susceptible to a number of soil fungi, including verticillium wilt, which causes ‘flagging,’ the loss of the tree limb by limb. Here is a description of it: https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-verticillium-wilt You can get testing to diagnose the problem at the OSU Plant Clinic: https://bpp.oregonstate.edu/plant-clinic I hope this is helpful. Good luck!

Tree decline may be due to a number of reasons. This page from the PNW Handbook describes possibilities, and in a street tree situation like this, hiring a certified arborist to evaluate trees is generally recommended. https://pnwhandbooks.org/plantdisease/pathogen-articles/common/tree-decline https://pnwisa.org/hire-an-arborist/

I was asked to comment on this question. I agree with the other two comments above (Vert wilt would be my first guess) but want to be thorough and ask additional questions. The thinning of the trees seem to always be on the same side, away from the street. Is the same compass direction such as south? Since the same kind of trees have the same problem on the same side we need to think about abotic problems. I can only guess pending more information but an example would be sunburn on the south side due to problems with watering?
Overall, please contact your communities street tree program or office that deals with street trees. They may know what is going on there and have solutions at hand or may not be aware of it at all. Either way, good to contact them.

I had a tree company come out and confirmed vert wilt, need to remove 3 trees and treat the remaining ones.

most of them have the problem on north side, away from the street. The same problem can be seen in neighborhood.